1. The characterization of novel epidermal growth factor receptor (EGFR) substrates, isolated by an expression cloning system was continued. the expression cloning method was described in a previous annual report. Analysis was focused on novel substrates: eps7, eps8, eps15 and eps27. 2. Analysis of the structure/function relationships of EGFR and gp185erbB-2 was also continued, focusing on the role of several domains in mediating receptor internalization. Results indicate that the introcytoplasm's domain of gp185erbB-2 does not possess the molecular signals necessary for rapid internalization, thus dictating a slow rate of removal of this receptor from the cell surface.